EDI (Electrodeionization) is a revolutionary water treatment
technology; it is a membrane filtration and desalination technology
that skillfully combined the electrodialysis technology and ion
exchange technology together, which is high-tech, green and
EDI equipment uses the RO outlet water as feed water. The
resistivity of RO outlet water is normally 40-2S/cm (25℃), and the
resistivity of EDI outlet water can normally reach 18M.cm (25℃).
According to the application of deionization water and the setup of
the system, EDI outlet water can meet the requirements for
resistivity of 1-18.2M.cm (25℃).
The advantages of EDI equipment are continual water production, no
acid and alkali regeneration, unattended operation, etc. It is
gradually replacing the mix bed as the fine treatment equipment.
Due to its environmentally friendliness and ease of use, EDI
equipment has been accepted by more and more people and widely used
in pharmaceutical, electronic, electricity, and chemical industry.
Its existence is a revolutionary progress of water treatment
equipment, which marked the water treatment industry finally
entered into green industry.
Advantages of EDI Equipment
EDI utilizes chemical-free regeneration method, which means a safer
workplace because there is no need to store or handle hazardous
acid and caustic. There are fewer regulation concerns due to the
absence of these corrosive chemicals and there will be no waste
neutralization or disposal issues.
EDI is a continuous process. The ion exchange resins are
continuously being regenerated by the DC electric field. There is
no excape of ions as happens in conventional ion exchange
operations, therefore the quality of the water remains at a
consistent high level of purity. The electric field also provides a
bacteriostatic environment inside the EDI cell, inhibiting the
growth of bacteria and other organisms.
EDI equipment has significantly lowered operating costs than
conventional ion exchange processes. Only a relatively small amount
of electric power is needed to complete the water purification. The
lack of acid and caustic regeneration means less operator attention
and lower labor costs. Capital costs can also be expected to be
lower, especially because no chemical storage, pumping and
neutralization equipment is required.
EDI equipment has a significantly smaller footprint than
conventional ion exchange equipment. This means that less plant
space will be required to provide the same quantity of water.
When to Consider Using EDI Equipment
EDI may be considered to be a competitive alternate process to
1. Regenerable mixed bed deionization
1) No acid or caustic bulk storage, pumping, waste neutralization
or disposal issues. 2) Lower operating cost due lower manpower
requirements as well as the lack of chemical regeneration. 3)
2. Service mixed bed deionization (off-site regenerated rental
1) No ionic breakthrough resulting in a constant high quality of
2) No rental vessels, associated freight or monthly demurrage
3. Second pass RO system
Eliminates the need for a second bank of RO membranes and
associated plumbing, pumping and control equipment.
Typical applications for EDI Equipment
Providing USP (United States Pharmacopeia) grade water
Feed to WFI (Water For Injection) stills
Steam Generation / Boiler Feed
Microelectronics / Semiconductor makeup and rinse water
For high quality makeup demineralized water
Hospital & university central systems
Advantages of EDI - Pharmaceutical Applications
EDI runs in a bacteriostatic service mode. The electric field
minimizes bacteria growth in the resin beds. Some EDI devices are
hot water sanitizable, resulting in more effective sanitization,
faster rinseup and more easily validated systems. RO/EDI easily
meets Stage 1 conductivity specification, while conventional 2-Pass
RO (RO/RO) does not, due to CO2 and/or NH3.
Advantages of EDI - Steam Generation Applications
EDI’s continuous electrochemical regeneration provides a constant
water quality with no escape of bands of ions. EDI is a low
maintenance process requiring little operator’s attention. EDI is
also ideal for remote locations where you might be dependent on
delivery of chemicals or DI tanks. EDI can provide low product
water conductivity, of much better quality then would be possible
with 2-pass RO alone.
Advantages of EDI - Microelectronics Applications